In the preparation of silver halide photographic emulsions, various additives are often used to change or improve photographic properties.
For instance, when methine dyes are employed at the time of preparing silver halide grains, they can cause change of size or size distribution in silver halide grains prepared. Further, by preparing silver halide grains in the presence of these compounds, it becomes possible to prepare grains difficult to produce under normal conditions such as AgCl grains having a (111) face, AgClBr grains having a (111) face, AgCl grains having a (110) face, AgClBr grains having a (110) face, AgBr grains having a (110) face and AgBrI grains having a (110) face, or to form grains having a (111) face under pAg conditions which theoretically only permits production of grains having a (100) face and to create the reverse of the above-described situation. Various crystal forms also become possible by this technique such as sticks, spheres and tabular forms. Specific examples are described in, for example, Japanese Patent Publication No. 42737/80, West German Patent Application (OLS) No. 2,932,185, Journal of Photographic Science, Vol. 21, p. 39 (1973), U.S. patent application Nos. 4,225,666, 4,183,756 and 2,735,766 and Unexamined Published Japanese Patent Application No. 23932/82. Further, the preparation of silver halide grains in the presence of methine dyes results in a remarkable increase of adsorption strength of the dyes on the grains. But at the same time, even if the so-obtained emulsions show excellent properties in terms of fog, sensitivity and tone gradation, because of the difficulty of desorption of the thus-employed dyes, the emulsions cannot be spectrally sensitized with dyes of other wavelengths. (That is, emulsions prepared using ortho dyes cannot be used as emulsions for regular wavelengths or panchromatic wavelengths.)
Further, even if silver halide emulsions of good monodispersibility or unusual crystal habits can be prepared by using desensitizing dyes, spectral sensitization cannot be performed unless the desensitizing dyes may be removed.
The silver halide emulsion grains which are obtained by using dyes vary over a wide range, and as a result, the desired silver halide emulsion grains cannot always be obtained with dyes of the desired spectrally sensitized wavelengths.
Moreover, when silver halide grains are prepared in the presence of dyes, even if the obtained grains have good monodispersibility or regular forms, there are cases where fog easily occurs due to the employed dyes, or subsequent chemical sensitization is strongly inhibited or marked development inhibition may occur during development.
On the other hand, photographically useful additives such as sensitizers and auxiliary agents to be used at the time of gold sensitization fully exert their effects at the time of or after the addition thereof in the course of preparing silver halide photographic emulsions to discharge their functions of changes or improvements in photographic characteristics. Thereafter, however, such additives become useless in most cases, and when remain in the silver halide emulsions, some of them do more harm than good to the photographic characteristics, to make matters worse.
As described above, the above-described various problems can be eliminated by speedily removing photographically useful additives after they are used for the preparation of silver halide emulsions, thus rendering them inactive.
Further, it is extremely difficult to completely remove and render inactive compounds having adsorption to silver halides by means of the above-described washing.
In particular, additives which have strong adsorption and which have strong effects on the formation of silver halide grains could not be removed by any known means.
In the light of the above-described circumstances, it has been strongly demanded to develop a system by which photographically useful additives can be smoothly removed and rendered inactive after they are used for the preparation of silver halide emulsions.